The present invention relates to a semiconductor device and a method of manufacturing the same. More particularly, the invention is concerned with a technique which is effective in the formation of a connection of wirings between different layers.
A semiconductor element and wiring, or wirings of different layers, are interconnected through a conductive film formed within a connecting hole. However, with microstructurization of semiconductor devices, studies are being made concerning a technique in which a portion, called a reservoir, is provided in an upper-layer wiring which overlies a connection. This technique is used for the following reason.
The reservoir represents a projecting portion (a surplus portion, a marginal portion) which is a part of the wiring and which projects from a wiring portion serving as a main current path. Although such a reservoir portion represents an unnecessary portion as a current path, it is formed for improvement of the electromigration (EM) resistance.
Electromigration is a phenomenon in which, when an electric current flows between upper- and lower-layer wirings through a connection, metal atoms which constitute the wirings and the connection migrate. As a result of this phenomenon, voids are formed within the wirings and the connection, causing a defective connection, such as breaking of the wire or a rise of the connection resistance.
However, if a reservoir is present, the reservoir serves as a metal atom supply source, whereby it is possible to decrease the rate of generation of voids and improve the electromigration resistance. Moreover, if a reservoir is present, it is possible to ensure a margin for pattern matching between wiring and a connection, whereby, even in the event of occurrence of mask displacement, it is possible to effect conduction between the wiring and the connection.
For example, Patent Literature 1 (Japanese Unexamined Patent Publication No. 2001-44196) discloses a technique in which a metallic reservoir 5a is provided above or below wiring to suppress the generation of voids caused by electromigration.
Further, Patent Literature 2 (Japanese Unexamined Patent Publication No. Hei 11(11999)-186433) describes the provision of a reservoir portion which improves the electromigration (EM) resistance.